Function _mmap_js

system/lib/wasmfs/syscalls.cpp:1606–1698

}

int _mmap_js(size_t length,
             int prot,
             int flags,
             int fd,
             off_t offset,
             int* allocated,
             void** addr) {
  // PROT_EXEC is not supported (although we pretend to support the absence of
  // PROT_READ or PROT_WRITE).
  if ((prot & PROT_EXEC)) {
    return -EPERM;
  }

  if (!length) {
    return -EINVAL;
  }

  // One of MAP_PRIVATE, MAP_SHARED, or MAP_SHARED_VALIDATE must be used.
  int mapType = flags & MAP_TYPE;
  if (mapType != MAP_PRIVATE && mapType != MAP_SHARED &&
      mapType != MAP_SHARED_VALIDATE) {
    return -EINVAL;
  }

  if (mapType == MAP_SHARED_VALIDATE) {
    WASMFS_UNREACHABLE("TODO: MAP_SHARED_VALIDATE");
  }

  auto openFile = wasmFS.getFileTable().locked().getEntry(fd);
  if (!openFile) {
    return -EBADF;
  }

  std::shared_ptr<DataFile> file;

  // Keep the open file info locked only for as long as we need that.
  {
    auto lockedOpenFile = openFile->locked();

    // Check permissions. We always need read permissions, since we need to read
    // the data in the file to map it.
    if ((lockedOpenFile.getFlags() & O_ACCMODE) == O_WRONLY) {
      return -EACCES;
    }

    // According to the POSIX spec it is possible to write to a file opened in
    // read-only mode with MAP_PRIVATE flag, as all modifications will be
    // visible only in the memory of the current process.
    if ((prot & PROT_WRITE) != 0 && mapType != MAP_PRIVATE &&
        (lockedOpenFile.getFlags() & O_ACCMODE) != O_RDWR) {
      return -EACCES;
    }

    file = lockedOpenFile.getFile()->dynCast<DataFile>();
  }

  if (!file) {
    return -ENODEV;